If you can remember that far back, you may remember that fish parasite was a member of the Copepoda, which is a group within the Crustacea. Most (although not all) copepods that parasitise fish are members of the Siphonostomatoidae and this week’s mystery object is part of that same Order.
Tony Irwin clearly knew the actual answer with a nicely crafted cryptic link to the two common sequential hosts of this animal, the Flounder and the Cod. Meanwhile, on Twitter there were another couple of suggestions – one was a good general biological principle:
Every time I see such weird stuff, I now apply a new biology rule I discovered : “If it doesn’t look like any living organism you know, if you even doubt it’s a real organism, then it must be a parasitic copepod”.
I’m struggling to accept it though. THOSE THINGS ARE ABSURD.
This is indeed a Codworm or Lernaeocera branchialis (Linnaeus, 1767) a type of copepod parasite that has a life history in which they spend part of their mobile larval stage parasitising flounders (and similar fish that sit around a lot) until they’re able to mate, at which point the fertilised female seeks out one of the mobile gadoid fish (the Cod family), where she gets into the gills and plumbs herself in to the Cod’s blood supply right at the heart, with her egg sacs at the gills and protected by the operculum (gill covers). She then spends the rest of her life sustained by fish blood, releasing eggs into the water and looking like a black pudding being eaten by maggots. Now those are life goals.
Adult female Codworm in Whiting gills. Image by Hans Hillewaert, 2006
I enjoyed the variety of entertaining answers, ranging from a preschool drawing of a grandma with a beehive hairdo to a larval Alien, but I was also impressed by the range of cryptic clues about the identity of the specimen.
A favourite was a reference to “dealing with a pea covering” or variations on that theme, which gives us “Cope” and “pod”, which is what this is – a Copepod (which means “oar-foot” in Greek). For those of you unfamiliar with copepods are small crustaceans, many of which live as zooplankton and that as a group may make up the majority of the Earth’s animal biomass. They’re tiny, but there are countless billions of them.
This one isn’t as tiny as many of its relatives, because it has a rather different lifestyle to planktonic forms. This is a sea louse and it’s a parasite of fish. They feed on the mucus, skin and blood of fish and if they reach high levels of infestation they can be a real problem, potentially killing fish. This particular specimen has two trailing egg cases, which I think threw some of you. It was removed from a Brill and as Daniel Calleri recognised from a visit to the Grant Micrarium, it’s Lepeophtheirus hippoglossi (Krøyer, 1837).
If you’ve been to the Grant Museum and have photos from the Micrarium, or if you have any photos of tiny animals, you might fancy entering a Twitter and Instagram competition by sharing them with the hashtag #MicroMultitudes, Have fun with your photos!
Last Friday Mark Carnall from the Grant Museum of Zoology provided a guest mystery object in the rather unpleasant looking form of this:
It looks a bit like part of a spinal column, but it isn’t. It looks like a worm of some kind, but it isn’t. So what is it?
David Craven and Dave Godfrey came through with the goods on this one. It is a parasitic crustacean related to the tongue worms (a misnomer because they are not worms at all) and it is in the genus Continue reading →